Is ablution considered valid if a flatus (a small, soundless, odorless farts) is expelled during ablution, with certainty of its expulsion, knowing that there is a continuous flatulence issue, and does the Hadith of the Messenger of Allah, peace and blessings be upon him: "He should not depart until he hears a sound or perceives a smell" apply in this case?

The emission of wind (flatulence) nullifies ablution, whether it is accompanied by a sound or not, and whether its odor is perceived or not. The decisive factor is the certainty of its emission. A person afflicted with continuous flatulence ( سلس الريح ) should perform ablution for prayer after the entry of its time, and he is not harmed by whatever exits from him during ablution or prayer. His ablution is nullified by anything other than this event.